Charles Durning's Journal --
Interesting Distributor Cap Problem or How a Simple Problem Can Snowball First let me say I’m a set it and forget it kind of guy. A few years ago I changed the distributor cap on my CBB GT to a side connection cap. The reason was to correct a problem with a too short oil cooler hose that was moving the cap as the engine moved. That solved the problem of the rotor hitting the internal contacts. The car has been running with no issues in the RPM range I use. The engine would fall on its face above 5K RPM. No problem since I never run it up there. Since I suspected the distributor was giving too much advance I completely removed the vacuum advance line and set the total advance at 35 degrees at 3300 RPM. Now the engine freely revs to 5500 RPM and wants more. A few years passed by and I decided to modify the carb air horns so the K&N RU-4410 air filters could slide on further and be more secure. When finished I went to the gas station and filled her up with non-ethanol gas and went for a spirited drive. During that drive the engine was no longer happy to rev freely. Given that we had lots of rain lately I figured I must have gotten a slug of water laced gas. I started the usual trouble shooting beginning with the fuel. No evidence of water in the float bowls. Since I haven’t had the plugs out in years, they were removed and looked good. Next I removed the distributor cap. AH-HA there was a burn through near one of the terminals in the cap. In addition it looked like the arc from the rotor as only going to the sides of the terminals in the cap. That must be the problem. Plugs, plug wires, cap, and coil were all changed since I had new in the gold mine, why not. Took the car for a spirited drive and no performance change for the better. A close inspection of the burned distributor cap revealed that the cap could be installed out of phase with the distributor. Apparently this cap could be secured with the usual clips and with screws. There is an additional relief by the screw holes that could locate the cap out of phase with the rotor. That must the reason for the spark arc to only jump to the side of the terminals in the cap. So what was the cause of the performance problem? There was nothing in the ignition that caused the oerformance problem, nor did I get a tank of bad gas. It was a misaligned gasket between the carb and the air horn. All is well now.
Posted 2021-09-01 09:27:13 by charles durning
Interesting Distributor Cap Problem or How a Simple Problem Can Snowball First let me say I’m a set it and forget it kind of guy. A few years ago I changed the distributor cap on my CBB GT to a side connection cap. The reason was to correct a problem with a too short oil cooler hose that was moving the cap as the engine moved. That solved the problem of the rotor hitting the internal contacts. The car has been running with no issues in the RPM range I use. The engine would fall on its face above 5K RPM. No problem since I never run it up there. Since I suspected the distributor was giving too much advance I completely removed the vacuum advance line and set the total advance at 35 degrees at 3300 RPM. Now the engine freely revs to 5500 RPM and wants more. A few years passed by and I decided to modify the carb air horns so the K&N RU-4410 air filters could slide on further and be more secure. When finished I went to the gas station and filled her up with non-ethanol gas and went for a spirited drive. During that drive the engine was no longer happy to rev freely. Given that we had lots of rain lately I figured I must have gotten a slug of water laced gas. I started the usual trouble shooting beginning with the fuel. No evidence of water in the float bowls. Since I haven’t had the plugs out in years, they were removed and looked good. Next I removed the distributor cap. AH-HA there was a burn through near one of the terminals in the cap. In addition it looked like the arc from the rotor as only going to the sides of the terminals in the cap. That must be the problem. Plugs, plug wires, cap, and coil were all changed since I had new in the gold mine, why not. Took the car for a spirited drive and no performance change for the better. A close inspection of the burned distributor cap revealed that the cap could be installed out of phase with the distributor. Apparently this cap could be secured with the usual clips and with screws. There is an additional relief by the screw holes that could locate the cap out of phase with the rotor. That must the reason for the spark arc to only jump to the side of the terminals in the cap. So what was the cause of the performance problem? There was nothing in the ignition that caused the oerformance problem, nor did I get a tank of bad gas. It was a misaligned gasket between the carb and the air horn. All is well now.
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Posted 2021-09-01 09:27:13 by charles durning
